F.D.A. Asks Pfizer to Add Viagra Warning on Vision Loss

Some blindness was reported by 38 men taking Viagra. The Food and Drug Administration said today that it had asked Pfizer Inc., the world’s largest drug maker, to amend its warnings on Viagra in response to scattered reports of vision loss by people taking the drug.

Some blindness was reported by 38 men taking Viagra – a tiny fraction of the 23 million people who have used the drug – and among four men taking Cialis, a newer competitor.

None of the 100 or so clinical trials on Viagra have suggested that the drug causes vision loss, but the F.D.A. said it had suggested updating the drug’s warning label as a precaution. The makers of Cialis, Eli Lilly & Company and the Icos Corporation, have already added such a warning.

Suzanne Trevino, a spokeswoman for the F.D.A., said that some of the patients who reported blindness might have been predisposed to it. "We’re not able to specifically say that these 38 cases are a result of the patients’ taking Viagra," she said. It is unclear whether men who take impotence drugs are any more likely than other men to develop the type of blindness reported, a disorder known as non-arteritic anterior ischemic optic neuropathy. NAION is common among people over 50 who have conditions like diabetes, heart disease, high blood pressure and high cholesterol – factors that also contribute to erectile dysfunction.

Pfizer said in a statement that dozens of clinical trials, involving 13,000 patients, had found no reports of such vision loss from taking Viagra, which has been on the market since 1998. "There is no evidence showing that NAION occurred more frequently in men taking Viagra than men of similar age and health who did not take Viagra," the company said.

John P. Mulhall, director of sexual medicine in the urology department of New York-Presbyterian Hospital/Weill Cornell Medical Center, provided support for Pfizer’s view. "It is entirely feasible that men who are at risk for NAION are at risk for erectile dysfunction and in fact are the people most likely to be using Viagra," he said.

Dr. Mulhall, who has advised several drug companies, including Pfizer, said that he had prescribed Viagra to at least 6,000 patients since 1998 and that none had reported vision loss.

Moreover, he said, patients who experience the visual problems that have long been associated with Viagra – blurred or bluish vision – are not necessarily more likely to lose their eyesight, because each response is caused in a different way.

The F.D.A. said Levitra, an impotence drug that is newer than Viagra and Cialis, had been linked to one such case. The drug is made by Bayer A.G. and GlaxoSmithKline P.L.C. and marketed by the Schering-Plough Corporation.